1. Field of the Invention
The present invention relates to an image pickup apparatus, such as a digital single-lens reflex camera, on which has a photographic lens is removably held.
2. Description of the Related Art
Conventionally, in an image pickup apparatus of the above-mentioned type, countermeasures are taken to prevent degradation of image quality due to dust attached to an optical member, such as a low-pass filter, disposed between a photographic lens and an image pickup element that converts light incident thereon from the photographic lens into an electric signal.
For example, an image pickup apparatus has been made commercially practical in which a member disposed between a photographic lens and an image pickup element is ultrasonically vibrated to thereby remove dust attached to the member. Further, there have been proposed an image pickup apparatus in which the number of times of attachment/detachment of a detachable low-pass filter is counted, and when the count reaches a predetermined value, cleaning of the low-pass filter is recommended (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. 2000-125152), and another in which a dust-removing mechanism is operated in response to the mounting of a photographic lens (see e.g. Japanese Laid-Open Patent Publication (Kokai) No. 2003-330082).
However, neither Japanese Laid-Open Patent Publication (Kokai) No. 2000-125152 nor Japanese Laid-Open Patent Publication (Kokai) No. 2003-330082 discloses a technique for coping with dust attached to a photographic lens mounted in a power-off state of the image pickup apparatus or with a battery removed from the apparatus. When considering situations in which image pickup apparatuses capable of exchanging photographic lenses are used, exchange of photographic lenses is performed more often in the power-off state than in the power-on state. However, in the image pickup apparatuses disclosed in the above-mentioned Patent Publications, in each of which mounting/removing of a photographic lens is electrically detected, it is impossible to detect the exchange of photographic lenses performed in the power-off state.
On the other hand, if the dust-removing mechanism is configured to be operated whenever the power is turned on, irrespective of whether or not a lens mounting/removing operation has been performed, an inconvenience occurs when the power is repeatedly turned on and off over a short time period without mounting or demounting a lens or when the apparatus returns from a sleep state (power-saving state where the operation of the apparatus is temporarily stopped) to an ON state. That is, the dust-removing mechanism is operated even when it is not required, which is undesirable in terms of power consumption and operation durability. Therefore, it is important to be able to detect, when the power is turned on again, whether or not a photographic lens-mounting/removing operation has been performed in the power-off state.